This invention relates to garage door openers, and more specifically to a safety circuit for a garage door opener control.
Garage door openers generally comprise a drive motor which is coupled to the door by means of a screw shaft or chain. In order to prevent injury to individuals who may be in the path of the door or to provent damage to the door or the drive system in the event an immovable object is encountered, most garage door opening systems include some mechanism for reversing the direction of the door operation in the event an object is encountered when the door is being lowered. In many garage door opening systems, the reversing apparatus consists of a mechanical device which senses a predetermined resistance to motor operations. Such devices become somewhat insensitive when applied to a door having a substantial frictional drag. In addition, conventional garage door opening devices do not reverse if an obstacle is encountered when the door is being opened. In addition, some conventional garage door openers suffer the disadvantage that safety systems are disabled if the transmitter or manual switches are held down.